The present invention relates to an apparatus for discharging liquid-covered particles from a reaction chamber and subsequent drying of said particles.
The present invention may preferably be used for removing liquid from liquid-atomized metal powder which gradually collects during the production process in the form of a slurry at the bottom of a reaction chamber. The invention will be described in the following with reference to this field of application without, however, being limited thereto.
The use of steel powders and other metal powders within the manufacturing industry has become more and more attractive. Thus the use of such metal powders for special purposes has particularly increased and recent attempts are made to produce metal powders with a certain conical form and certain size distribution in direct connection with conventional steel plants. However, such local manufacturing of special metal powders has up to now been impossible to realize under economic conditions by using known technology, due to the fact that the discharging of such produced metal powders from the reaction chamber and the following drying operation required therewith has necessitated extensive, technically complicated auxiliary equipment.
At present reaction chambers are used for the production of such metal powder, comprising a granulation chamber in which a casting ladle is arranged at the upper part of the chamber. The molten metal is poured from this casting ladle through a bottom opening and is then brought into contact with an atomizing medium flowing at high-speed, which disintegrates the casting jet into fine drops. For metal powder in which a low oxygen content is desired, the liquid-atomization is performed in reducing environment and a hydrocarbon compound or some other similar liquid is used as atomizing medium. This liquid together with the powder is collected at the bottom of the reaction chamber in the form of a slurry.
According to conventional technology the discharging and subsequent drying of the metal powder is performed in batches, i.e. the entire quantity of slurry in the reaction chamber is tapped off and transported to a plant with a vacuum filter or the like where most of the liquid is separated off and the powder is then transported to a drying plant, drying usually being performed by means of hot, flowing air. However, such a drying procedure is extremely time-consuming and thus also expensive, primarily due to the fact that the production in the reaction chamber must be interrupted every time a discharge operation is performed. Environmental problems are also considerable since work is first carried out in a wet or moist environment and thereafter in an extremely dry environment with free access to the air. There is also considerable risk of the metal powder being subjected to undesired oxidation.